Relay apparatus

ABSTRACT

A relay apparatus to operate in response to an induction from an electric current in a conductor and including a housing having a first contact mounted thereon. A flexible blade is carried by one end from the housing and carries a movable contact on its free end. Sensing means is responsive to a predetermined electrical current in the lead to provide a signal which is amplified to operate an actuator which flexes the blade to engage the movable contact with the first contact. The blade may be of nonlinear configuration and the actuator may move transversely thereto and engage such blade intermediate its ends to cause flexing thereof to engage the movable contact with the stationary contact and to continue flexing of such blade to move the movable contact across the surface of the first contact whereby the blade will remain flexed during contact closure and will tend to unflex when the actuator is retracted to apply a shearing force to any weld that may have developed between the contacts to thereby break such weld.

United States Patent McIntosh et al.

[ Jan. 18, 1972 4] RELAY APPARATUS Primary ExaminerL. T. Hix [72]inventors: Harold A. McIntosh, South Pasadena; Hol- Ammey FulwlderPatton Lee & Utecm its L. Randolph, Lakewood; William W. Chambers,Anaheim; Marvin M. Graham,

Seal Beach, all of Calif.

Assignee: Robertahaw Controls Company,

Richmond, Va.

Filed: Jan. 28, 1970 Appl. No.: 6,529

U.S. Cl ..317/l48.5 B, 335/204, 307/131, 317/D1G. 9 Int. Cl ..H0lh 9/00,l-lOlh 47/32 Field of Search ..317/l37, D16. 9, 148.5, 148.5 B; 336/105;307/131; 335/204 References Cited UNITED STATES PATENTS 3,419,75612/1968 Philbert et a1. ..317/16 [57] ABSTRACT The blade may be ofnonlinear configuration and the actuator may move transversely theretoand engage such blade intermediate its ends to cause flexing thereof toengage the movable contact with the stationary contact and to continueflexing of such blade to move the movable contact across the surface ofthe first contact whereby the blade will remain flexed during contactclosure and will tend to unflex when the actuator is retracted to applya shearing force to any weld that may have developed between thecontacts to thereby break such weld.

16 Claims, 26 Drawing Figures PATENTEI] JAN18EJ72 3.636.414 sum 2 -.or.33

.53 l VENT :36 Z Hm, mafia 57 HOLLIS 1.. RANDOL PH (4/ 24/ 7 BY WILL/AMMl, Cl/IMBEEJ F v MAI VIN M.

RELAY APPARATUS BACKGROUND OF THE INVENTION I Field of the Invention Thepresent invention relates to a relay which is responsive to apredetermined current in an electrical lead to actuate an operatorcircuit and which may employ a switch having con-' tacts which are slidon one another when the switch is opened to thereby shear any weld whichhas been developed therebetween.

2. Description of the Prior Art Current-sensing relays known toapplicants frequently provide insufficient power to operate the relay ina circuit having a relatively large load thereon. Further relays havebeen proposed which include means for moving one contact across thesurface of the other when the relay is deenergized to thereby break anyweld formed between the contacts, but these relays generally employcams, or linkages to effect the sliding between thecontacts therebyresulting in a requirement of relatively large forces for operation.Also, many relays of this type are of such configuration that currentconduction through the switch is relatively poor. Relays have beenproposed which include flexible blades afiixed on one end to the relaybody and carrying a movable contact intermediate its ends and projectingtherebeyond to form an overhang which is engaged by a transverselymoving actuator to close the contacts and slide one relative to theother. However, such an arrangement does not provide sufficient contactsliding for many applications.

SUMMARYOF THE INVENTION The relay of'present invention ischaracterizedby a movable contact carried from a blade for selectiveengagement with a stationary contact. A sensing means is responsive to apredetermined current in an electrical lead to actuate an amplificationmeans which operates an actuator coupled to such blade to thereby closethe switch.

The blade, is preferably flexible and of nonlinear configuration and isaffixed on one end to the housing and has the movable contact carriedfrom its free end. The actuator engages the blade intermediate its endsand has sufircient travel transverse to the blade after the contacts areengaged to flex and partially straighten the blade to cause sliding ofthe movable contact on the stationary contact whereby when the actuatoris deenergized to enable the relay to open the blade will tend to slidethe movable contact across the stationary contact to breakany weld thatmay have developed between the contact An object of the presentinvention is to provide a relay of the type described which has arelatively high current rating and requires a relatively low amount ofpower for operation.

Another object of the present invention is to provide a relay of thetype described wherein the blade carrying the movable contact serves asa current carrying member and, while providing relatively low springtension, provides sumcient cross-sectional area to avoid electricalheating-during conduction of current therethrough.

It is a further object of the present invention to provide a relay ofthe type described wherein the opening forces are utilized to causesliding of the contacts on one another rather than providing for arocking movement between such contacts, it being noted that any weldaccidentally formed between the contacts would be weakest in shear.

A further object of the present invention is to provide a relay of thetype described wherein the fixed end of the blade is mounted from thecontact housing at a point offset from the plane of the stationarycontact to thereby enhance the tendency of the movable contact to slideon the stationary contact when the actuator is deenergized and the bladeunflexes.

It is still another object of the present invention to provide a contactof the type described wherein the con cts will not bounce apart uponinitial engagement thereof to thereby avoid arcing and consequentwelding therebetween.

It is a still further object of the present invention to provide a relayof the type described wherein the contacts are slid across one anotherduring making and breaking thereof to wipe the surface oxides andimpurities to maintain good contact and, consequently, good electricalconduction therebetween when the contacts are closed. Such wiping actionalso tends to maintain the contact surfaces smooth thereby avoiding anytendency of the contacts to lock together due to interlocking irregularcontacting surfaces. Further, the sliding of the contacts wipes anydielectric film from between the contacts.

These and other objects and the advantages of the present invention willbecome apparent from the consideration of the following detaileddescription when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 7 is a horizontal sectional view takenalong the line 7 7 of FIG. 4; 1

FIG. 8 is a vertical sectional view taken along the line 88 of FIG. 3;

FIG. 9 is a vertical sectional view taken along the line 99 of FIG. 2;

. FIG. 10 is a vertical sectional view taken along the line I0 10 ofFIG. 2; I

FIG. 11 is a horizontal sectional view taken along the line ll-ll ofFIG.4;

FIG. 12 is a horizontal sectional view taken along the line l2l2ofFlG.ll;

FIGS. 13 through 16 are diagrammatic views, in enlarged scale, of aflexible blade carrying the movable contact included in the relay shownin FIG. 1, such blade being shown in several different positions;

FIG. 17 is an electrical schematic of a circuit which may be utilizedwith the relay shown in FIG. I;

FIG. 18 is a vertical sectional view of a second embodiment of thecurrent-sensing relay of present invention;

"FIG. 19 is a vertical sectional view taken along the line 19- 19 ofFIG. 18;

FIG. 20 is a horizontal sectional view taken along the line 20-20 ofFIG. 18;

FIGS. 21 through 24 are diagrammatic views showing the contact-carryingblade in several different positions; and

FIGS. 25 and 26 are diagrammatic views of modifications of thecurrent-sensing relay shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 3, thecurrent-sensing relay of present invention includes, generally, ahousing 31 which has one end of a flexible electrically conductivearcuate blade 35 (FIGS. 13-17) mounted thereon and carrying a movablecontact 37 on its free end for engagement with a stationary contact 39disposed thereunder. The arcuate blade 35 is engaged intermediate itsends by the lower end of a spacing post, generally designated 43,interposed between such blade and the free end of a cantileverallymounted, ferromagnetic arm 47 (FIGS. 3 and 17). An actuator coil 51 isdisposed under the inter mediate portion of the ferromagnetic arm 47 andhas current thereto controlled by the power circuit of asilicon-controlled rectifier (SCR) 53. The gate of the SCR 5 3 isconnected with dary coil 57 will impose a triggering current on the gateof the SCR 53 to initiate current through the actuator coil 51 toattract the arm 47 and push the blade 35 downwardly to the positionshown in FIG. 13. After the contacts 37 and 39 engage, the actuator coilcontinues to attract the arm 47 downwardly to flatten the flexible blade35 to the position shown in FIG. 14 thereby sliding the movable contact37 to the left on the primary contact 39 to provide a wiping actionbetween the contacts and maintain the flexible blade in such flattenedposition until the relay is deenergized. When current in the leads 65drops below the actuation level, the SCR 53 will be renderednonconductive thereby discontinuing current in the coil 51 and enablingthe flexible blade 35 to unflex and force the movable contact 37 to theright on the stationary contact 39 as shown in FIG. thereby effecting ashearing action between such contacts to shear any weld that may havebeen formed therebetween.

Referring to FIGS. 1 through 5 the housing 31 includes a plastic base 75which is formed with a bottom wall 76 and a pair of opposed upstandingsidewalls 77 and 79. A cover, generally designated 81, is received onthe base and includes a top wall 83 formed with a pair of downwardlyextending opposed end walls 85 and 87 which cover the open ends of thebase and are formed on their marginal edges with inwardly bentperipheral lips 91 which overlie the marginal ends of the respectivesidewalls 77 and 79. Referring to FIG. 1, the end wall 87 is fonned withoppositely projecting mounting tabs 80 and 82 for mounting the relay toa wall. As best seen in FIGS. 1 and 4, the cover 81 is also formed withdownwardly bent ears, generally designated 93 and 95, that are injuxtaposition with the base sidewalls 77 and 79 and out of which arepressed upwardly projecting and inwardly bent resilient holding tabs 97and 99, respectively, which engage in depressions .101 and 103 formed inthe respective sidewalls 77 and 79 and abut against the upper endsthereof to hold the cover 81 securely on the base.

Referring to FIGS. 3 and 13, the fixed end of the flexible blade 35 isturned back under itself and forms a mounting tab 105 which has amounting tab 106 of a terminal, generally designated 107, extendingthereover and secured in position by a rivet 109. The terminal 107 hasits one extremity bent downwardly and extends through a passage 110 inthe bottom wall 75 of the base and extends therebelow to form a plugprong I13.

Referring to FIG. 12, the passage 110 is formed on one side with areduced-in-cross-section keyway 111 and the downwardly bent plug prong113 is formed with a reduced-incross-section key 115 which interfits thekeyway I11 whereby the downwardly turned terminal prong 113 may beinserted downwardly through the passage 110 and the entire terminal 107then shifted sideways to fit the key 115 in the keyway 111. Then whenthe rivet 109 is inserted the terminal 107 will be held firmly inposition with the key 115 held captive in the keyway 11.

Referring to FIG. 2, the stationary contact 37 is carried from aterminal, generally designated 121, similar to the terminal 107 andformed with a downwardly projecting plug prong 123 which is formed witha key similar to that shown in FIGS. 11 and 12 for interlocking with acooperating keyway in the bottom wall 75 of the housing base. Stillreferring to FIG. 2, a stationary contact 125 is disposed above and inalignment with the movable contact 37 and is carried from a terminal,generally designated 127, which is formed with a downwardly projectingplug prong 129 having a key similar to that shown in FIG. 11 formedtherein for interfitting a cooperating keyway in the base bottom wall73.

Referring to FIGS. 2 and 17, the rear end of the actuating arm 47 rideson the top of a vertical support post defined by one leg 131 of ahorseshoe-shaped magnet, the other leg of which defines a core 153 forthe relay coil 51. The post 131 is formed with a pair of transverselyaligned outwardly opening notches 135 (FIG. 4) and with a rearwardlyopening central notch 137. A resilient retaining clip, generallydesignated 141, (FIG. 2) extends upwardly along the backside of the post131 and is formed with a pair of transversely spaced upwardly projectingears 143 which are received in the side opening notches 135. The clip141 is formed with a retaining tab 147 that is offset rearwardly fromthe body of the clip and projects upwardly through the central notch 137and is then bent forwardly over the rear extremity of the arm 47 andturns downwardly to engage such arm in front of the post 131 to maintainthe forward extremity of such arm biased downwardly.

The actuator coil 51 is disposed centrally under the arm 47 and, asindicated above, has its central core formed by the magnet leg 153(FIGS. 2 and 7), the upper extremity of which leg serves as a stop forthe intermediate portion of the arm 47 to positively limit downwardmovement of the free extremity thereof. Still referring to FIG. 7, thecentral portion of the arm 47 is formed with upwardly and outwardlyflared wing portions 155 to form a central downwardly projecting apex157 that engages the stop defined by the upper extremity of the core153.

Referring to FIG. 6, the underside of the rear extremity of the arm 47is formed with a downwardly opening recess 159 that defines a pair ofdownwardly projecting legs I61 and 163 disposed on opposite sidesthereof and which ride on the upper end of the support post 131 wherebythe rear extremity of the arm 47 will be supported from such legs 161and 163 and the forward extremity supported by the apex 157 (FIG. 7)when the arm 47 is pulled downwardly to thereby provide a stable threepoint support to prevent rocking and tilting thereof.

The spacing post 43 interposedbetween the actuating arm 47 and theintermediate portion of the blade 35 includes an upwardly projecting peg143 (FIG. 3) received in an elongated slot 145 (FIG. 4) formed in thefront extremity of such arm and a downwardly projecting peg 147 (FIG.13) received loosely in a bore through the blade 35 to thereby providefor shifting of the free end of such blade relative to the arm 47 assuch blade is flexed.

Referring to FIGS. 1 and 8, the retaining bale 61 is generally U-shapedand has its opposite legs projecting through slots formed in oppositesides of the top wall 83 of the cover 81, such legs projectingdownwardly and being formed with through downwardly opening slots 17]and 173 that define forks which receive opposite extremities of amagnetically conductive mounting bar, generally designated 175, disposedwithin the cover 81. Theend walls 85 and 87 are fon'ned with respectiveslots 177 and 179 and the opposite extremities of the mounting barextend through the slots 171 and 173 in the loop 64 and the forksdefined by the extremities of the loop are pinched closed thereon. Theends of the mounting bar 175 project beyond the slots 177 and 179 in thecover 81 and are staked over on their projecting extremities forpositive retention.

Referring to FIGS. 2, 5 and 8, a bobbin, generally designated 183, isformed from a synthetic plastic and includes a hollow central passage(FIG. 8) for receipt of the mounting bar 175 and has external flanges187 and 189 which are spaced apart to define a spool 191 therebetweenfor receipt of the windings of the secondary coil 57 included in thesensing transformer 59.

Referring to FIG. 5, the flanges 187 and 189 are each formed on theirone side with respective projecting ears 193 and 195 which are formedwith open-ended retaining notches that receive and frictionally holdrespective leads 197 and 199 of a resistor 201 utilized in the circuitryfor the relay. The bobbin 183 includes a pair of laterally projectingopposed jaws 205 and 207 for receipt therebetween of the SCR 53 and areformed on their respective projecting extremities with inwardly turnedconfronting lips 211 and 213 for retention of such SCR. Projectingopposite the jaws 205 and 207 are opposed inwardly tumed resilientflanges 217 and 217 (FIG. 3) which receive a resistor 219 therebetween,such resistor also being utilized in the control circuitry.

Referring to FIGS. 2 and 10, a coil terminal, generally designated 225,is disposed adjacent the actuator coil 51 and is connected with one endthereof. The terminal 225 projects downwardly through a passage 229included in the bottom wall 76 of the base, such passage being formed onits upper extremity with oppositely angled flares 231 and 233. Theterminal 225 is somewhat malleable and includes a pressed outperpendicularly projecting portion defining a limit tab 226 for engagingone side of the housing wall 76. Such terminal 225 is formed with areduced-in-cross-section area 235 to form oppositely disposed notchesfor receipt of a staking tool whereby such terminal may be inserted inthe passage 229, the tab 226 engaged with one side of the wall 76 andthe terminal staked over to-form oppositely extending rivet portions 237and 239 which engage the flares 231 and 233, respectively, to retainsuch terminal in position.

Referring to FIGS. 4 and 17, a second coil terminal 240,

similar to the terminal 225, is connected with the anode of the SCR 53.One end of the resistor 201 (FIG. 5) is connected with a manual switchterminal, generally designated 24], which is formed with areduced-in-cross-section area 243 for receipt in a through passage 245in the bottom wall 76 of the housing base. The upper extremity of thepassage 245 is formed with oppositely angled flares 246 and 247 and theupper extremity of the terminal 241 is split for spreading to formoppositely angled retaining legs 248 and 249 which cooperate with theshoulder 250 formed by the bottom end of the reduced-incross-sectionarea 243 to retain such terminal in the housing base.

The electrical schematic shown in FIG. 17 depicts an electrical circuitwhich may be employed with the relay of present invention and includes atransformer 251 having its primary coil in circuit with a source plug252 and its secondary coil connected in series with the power circuit ofthe SCR 53 and with the actuator coil 51. A capacitor 253 is connectedacross the secondary coil of the transformer 251 to control the voltagespikes.

A freewheeling resistor 257 is connected across the actuator coil 51 toprovide a path for current flow during nonconductive portions of the SCRcontrolled or current cycle to thereby reduce hum.

Connected in parallel with the gate of the silicon-controlled rectifier53 is the resistor 201 which leads to the terminal 241 for connectionwith one side of a manual switch 263 by means of a lead 262. The otherside of the switch 263 is connected with the side of the secondary coil57 opposite the cathode of the SCR 53 whereby such SCR may be triggeredby closing of such manual switch 263.

When the relay is assembled, the base and cover 81 are formed separatelyand the terminals 107, 123, 129, 225, 240 and 241 are installed asdescribed above. The bobbin 183 serves as a jig for winding the coils ofthe secondary coil 57 of the sensing transformers 59 thereon and forholding the SCR 53 and resistors 201 and 219 during soldering of theleads thereof. First the secondary coil 57 is formed by wrappingwindings on the spool 191 and the SCR 53 may then be inserted betweenthe flexible jaws 205 and 207. The resistor 2.01 may then be positionedadjacent the secondary sensing coil 57 with its terminals receivedbetween the jaws defined by the projecting tabs 193 and 195 (FIG. 5).The resistor 219 is then inserted between the jaws 215 and 217 (FIG. 3)and the respective terminals are bent to the general configuration shownin FIG. 5 and the electrical leads between adjacent elements soldered.In this manner the bobbin 183 serves as a jig for holding the electricalcomponents in position while their terminals are soldered to therespective leads.

The assembled relay is particularly useful for controlling a fan forblowing air over a plurality of independently actuated resistanceheating elements and may be installed on a wall adjacent a furnaceincluding such elements by inserting mounting screws through themounting cars and 82 (FIG. I). A socket assembly, or assemblies, formedwith receptacles for the respective plug prongs of the terminals 107,123, 225, 240 and 241 may then be mated with such terminals to connectthe terminals 123 and 107 with a blower for blowing air over a pluralityof heating elements 267, the terminals 225 and 240 with the sourcetransformer 251 and the terminal 241 with the manual switch 263. Theleads 65 to the independently actuated heaters are then threaded throughthe retaining bale 64.

When any one of the furnace heating elements 267 is energized thecurrent in the electrical lead 65 thereto will induce a current in thesecondary coil 57 of the sensing transformer 59 to impose a triggeringsignal on the gate of the SCR 53 thereby energizing the actuator coil 51to pull the free end of the actuator arm 47 downwardly. Downwardmovement of the free end of the actuator arm 47 will pivot the flexiblearm 35 about its right-hand end, as shown in FIG. 13, to cause themovable contact 37 to travel in a path somewhat oblique to thestationary contact 39 to thereby avoid direct striking thereof andconsequent bouncing apart of the contacts which may result in arcingwhich may cause contact deterioration and possible welding together.Continued downward movement of the free end of the actuator arm 47 underthe influence of the actuator coil 51 will cause the generally arcuatelyshaped flexible blade 35 to flatten somewhat to the position shown inFIG. 14 thereby moving the movable contact 37 leftward across thesurface of the stationary contact 39 to provide a wiping action andcause the blade 35 to assume and maintain a stressed positron.

It is noted that travel of the free end of the arm 47 generallytransverse to the blade 35 will be multiplied by the flattening of suchblade to produce a greater amount of sliding of the movable contact 37on the stationary contact 39 over that which would be provided by anequivalent amount of transverse travel of the central portion of astraight blade. Numerous blade configurations may be employed forproviding similar results, some of which are shown in FIGS. 25 and 26.

It will be clear from FIG. 2 that the cantilever mounting of the arm 47enables the intermediate portion of such arm to be spaced relativelyclose to the actuator coil core 153 to provide a relatively small airgaptherebetween whereby energization of such core will strongly attract theintermediate portion of said arm thereby effecting a relatively largemovement of the free end of the arm to effect relatively large downwardmovement of the intermediate portion of the flexible blade 35 to closethe contacts and effect a relatively large amount of travel of themovable contact 37 across the surface of the stationary contact 39.

It is important that in its actuated position the actuator arm 47 issupported at its rear extremity from the top end of the vertical post131 (FIGS. 4 and 6) by means of the downwardly projecting legs 161 and163 and is supported intennediately on the top end of the actuator coilcore 153 by means of downwardly projecting apex 157 to thereby assure anessentially three point support to provide a relatively stable conditionfor the actuator arm 47 thereby avoiding rocking thereof andconsequently erratic operation.

It is also of importance that the apex 157 is somewhat elongated in thelongitudinal direction of the arm 47 to provide a wearing surface thatis relatively large while providing for contact with the core 153 alonga line extending longitudinal to such arm. The chevron or somewhatV-shape presented by the upwardly and outwardly angled wings (FIG. 7)provides a configuration wherein the magnetic flux from the coil 51 willbe heavily concentrated at the apex 157 thereby leaving only arelatively small portion of the total flux to assume a path through theairgap formed between the angled wings I55 and the top of the core 153.It is noted that the magnetic attraction of a body is inverselyproportional to the square of the distance of such body from themagnetic source. Thus wearing of the apex 157 which causes the arm 47 tobe positioned closer to the core 153 when the relay is actuated has onlya minor effect on the composite airgap between the arm 47 and top of thecore 153 thereby only slightly altering the magnetic attraction of thearm 47 to provide only a minor change in the operating characteristicsof the relay. When the current in all the leads 65 from the respectivefurnace elements 267 is discontinued, the current on the gate of the SCR53 will drop below the triggering level to thereby block current flowthrough the actuator coil 51 and release the arm 47 for upward pivotingof its free end under the influence of the flexible blade 35. Theintermediate portion of the arcuate flexible blade 35 is then free toflex upwardly and draw the movable contact 37 across the surface of thestationary contact 39 as shown in FIG. 15. It is important that theentire initial movement of the movable contact 37 is linear travelacross the surface of the stationary contact 39 to thereby utilize theentire unflexing force of such blade to shear any weld which may havebeen formed between such contacts. This is important because. such aweld would be weakest in shear.

Sliding movement of the movable contact 37 caused by unflexing of thespring blade 35 to its arcuate position is further enhanced by the factthat the free end of such blade tends to pivot upwardly and to the rightabout the fixed right-hand end of such blade (FIG. to thereby produce anadditional component of travel to the right over that which would beprovided by a blade having its fixed end disposed in the same plane asthe free end.

If at any time it should be desirable to actuate the blower (not shown)when the heater elements 267 are not energized, the manual switch 263may be closed to provide current flow through the resistor to produce atriggering current at the gate of the SCR 53 to energize the actuatingcoil 51 and repeat the above described contact closure.

The current-sensing relay shown in FIGS. 18 through 24 is similar tothat shown in FIG. 1 except that the relay coil 275 is disposed abovethe actuating arm 47 and is carried from the housing by means of amounting bracket 77. The core of the coil 275 is in the form of aninverted horseshoe 281 and the rear extremity of the actuating arm 47 isbiased upwardly against one leg thereof by means of a retaining clip,generally designated 285, which is similar to the retaining clip 141 butpartially inverted.

The free end of the actuating arm 47 carries a post, generallydesignated 289, which is connected with the intermediate portion of theelectrically conductive r'esilient blade 35. Thus, when the coil 275 isenergized, the free extremity of the arm 47 will be moved upwardly topull the movable contact 37 upwardly into engagement with the stationarycontact 125 and continued upward flexing of the central portion of theblade 35 will flex such blade to a more arcuate configuration and slidethe movable contact 37 to the right across the surface of the stationarycontact 125 as shown by the directional arrows in FIG. 22. When therelay coil 275 is deenergized, the arm 47 will be released and theflexible blade 35 will unflex to slide the movable contact 37 to theleft across the stationary contact 125 as shown in FIG. 23 to therebybreak any weld that may have developed between such contacts. Obviously,both the upper and lower stationary contacts 125 and 39 may be utilizedin a control circuit.

The blade configurations 35' and 35" shown in FIGS. 25 and 26 arerepresentative of other blade configurations which would provide slidingof the respective movable contacts 37 and 37" on respective stationarycontacts 39' and 39" when a transverse actuating force is applied tosuch blade after initial contact engagement has been made.

From the foregoing detailed description it will be apparent that thecurrent-sensing relay of present invention is straightforward inconstruction to provide a convenient and compact package which isrelatively inexpensive to produce. The base and cover form a housingwhich is convenient to assemble and means is provided for convenientlysecuring the plug prongs in position in the base. Further, the bobbinfor the secondary sensing coil provides a spool for such coil and formsa relatively convenient jig for mounting the electrical componentsduring connection together thereof. Further, the elongated actuating armis cantileverally mounted and the actuating coil core, which acts as astop to limit downward travel of such arm, is disposed intermediate theends of such arm to provide a relatively small airgap between such coiland arm to enhance the magnetic attraction therebetween and to enablesuch stop to act on a portion of the arm which travels through arelatively short arc to thereby reduce relay noise during activationthereof. In addition, the nonlinear configuration of thecontact-carrying blade provides a transverse force which causes slidingof the movable contact on the stationary contact upon deactuation of therelay and the consequent wiping polishes the engaging contact surfaceseach time the relay is actuated to thereby remove dielectric film andmaintain the contact surfaces smooth to prevent mechanical hanguptherebetween.

Various modifications and changes may be made with regard to theforegoing detailed description without departing from the spirit of theinvention.

What is claimed is:

l. A current-sensing relay for operating in response to a predeterminedelectric current in a lead, said relay comprismg:

a housing including a ferromagnetic loop formed with a ferromagneticbar;

a first contact mounted on said housing;

a movable contact disposed in engageable alignment with said firstcontact;

a blade carrying said movable contact;

electrical actuator means for moving said blade to selectively engageanddisengage said contacts;

sensing coil means wound on said bar and mounted in circuit with saidactuator means for sensing the current in said lead and responsive tosaid predetermined electrical current to produce an electrical signal;

amplifier means in circuit with said actuator means and sensing meansand responsive to said signal to operate said actuator means and movesaid blade whereby said relay will operate in response to saidpredetermined electrical current.

2. A current-sensing relay as set forth in claim I wherein:

said blade is elongated, flexible and crooked and has one end affixed tosaid housing and carries said movable contact on its free end; and

said actuator means operatively engages said blade intermediate said oneend and said movable contact to move said free end transversely andengage said movable contact with said first contact, and then continuetransverse movement of the intermediate portion of said blade to furtherflex said blade and slide said movable contact across said first contacta sliding distance greater than it would be slid by an equivalent amountof transverse movement of the intermediate portion of a straight bladewhereby when said actuator is released said blade will unflex and movesaid movable contact said sliding distance across said first contact toprovide a relatively large contact breaking force.

3. A current-sensing relay as set forth in claim 1 wherein:

said amplifier means includes a silicon-controlled rectifier having itsgate in circuit with said sensing means and its power circuit in circuitwith said actuator means.

4. A current-sensing relay as set forth in claim 1 wherein:

said actuator means includes an arm having its front extremityprojecting over said blade for engagement therewith, a mount carried onsaid housing for supporting the rear extremity of said arm and includinga resilient holding clip projecting forwardly over the rear extremity ofsaid arm and beyond said mount to bias said front extremity downwardlytoward said blade.

5. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a terminal receiving passage formed with adepression in one side for defining a keyway; and

said relay includes a plug terminal in circuit with one of said contactsand projecting through said passage to form a plug prong, said terminalbeing formed with a reduced-incross-section portion defining a key forcomplimentally interfitting said keyway whereby said terminal may beinserted in said passage, shifted laterally therein to fit said key insaid keyway, and affixed to said housing to mount said terminal firmlyon said housing.

6. A current-sensing relay as set forth in claim 1 wherein:

said housing is formed with a terminal receiving passage;

and

said relay includes a terminal for insertion in said passage andincluding a malleable rivet forming portion whereby said terminal may beinserted in said passage and said rivet forming portion riveted over tohold said terminal captive in said passage. 7

7. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a base formed with a pair of oppositely disposedsidewalls formed on their exterior with respective clip-receivingrecesses, said housing further ineluding a cover formed with a pair ofoppositely disposed downwardly projecting sidewalls in juxtapositionwith the walls of said base and formed with resilient clips for receiptin said recesses to lock said cover to said base.

8. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a blade mount;

said actuator includes an an'n formed on its rear extremity with a pairof spaced apart legs carried on said mount, and is formed intermediatelywith a downwardly projecting apex; and

said housing includes a stop disposed adjacent said apex for engagementthereby to limit travel of said arm toward its contact closing positionwhereby said arm will be supported at three points when said relay isactuated.

9. A current-sensing relay as set forth in claim 1 that ineludes:

a bobbin fonned with a spool for winding said coil thereon and with apassage extending through the center of such spool for receipt of amagnetic conductor disposed in electrical inductive relationship withsaid lead.

10. A current-sensing relay as set forth in claim 2 wherein:

said blade is formed intermediately with a peg-receiving opening; and

said actuator means includes a peg which loosely interfits said openingwhereby the intermediate portion of said eludes:

blade will be free to shift forwardly and rearwardly during actuation ofsaid relay to facilitate alignment between said blade and actuator.

11. A current-sensing relay as set forth in claim 1 wherein:

said housing includes a mounting bar having its opposite ends connectedwith said loop and having said coil wound therearound.

12. A current-sensing relay as set forth in claim 11 wherein:

said housing is formed with a pair of slots for receiving the oppositeextremities of said loop;

said loop is generallyU-shapcd and has its opposite extremitiesprojecting through said slots and said opposite extremities are fonnedwith openings; and

the opposite extremities of said mounting bar project through saidopenings and are secured to said housing to affix said loop to saidhousing.

13. A current-sensing relay as set forth in claim 9 wherein:

said actuator means includes a plurality of electrical components; and

said bobbin includes a plurality of holding tabs forming cavities forreceipt of said respective components.

14. An electrical switch as set forth in claim 1 wherein:

said actuator means includes an electromagnet having its core formed onone end with a stop, an arm coupled with said blade and overlying saidcore and formed with a V- shaped ferromagnetic portion disposed adjacentsaid stop and having its apex engageable therewith when saidelectromagnet is energized whereby said V-shaped portion will form aplate for a relatively lar e portion of the magnetrc flux from saidelectromagnet t ereby leavmg a relatively small portion of the magneticflux to assume a path across the composite airgap between said V-shapedportion and said stop.

15. A current-sensing relay as set forth in claim 1 that ina secondcontact mounted from said housing, disposed on the opposite side of saidblade from said first contact, and in engageable alignment with saidmovable contact.

16. A current-sensing relay as set forth in claim 1 that ineludes:

an auxiliary plug terminal mounted on said housing and connected incircuit electrical actuator for connection to a lead from an auxiliaryactuator whereby said relay may be actuated by said auxiliary actuator.

1. A current-sensing relay for operating in response to a predeterminedelectric current in a lead, said relay comprising: a housing including aferromagnetic loop formed with a ferromagnetic bar; a first contactmounted on said housing; a movable contact disposed in engageablealignment with said first contact; a blade carrying said movablecontact; electrical actuator means for moving said blade to selectivelyengage and disengage said contacts; sensiNg coil means wound on said barand mounted in circuit with said actuator means for sensing the currentin said lead and responsive to said predetermined electrical current toproduce an electrical signal; amplifier means in circuit with saidactuator means and sensing means and responsive to said signal tooperate said actuator means and move said blade whereby said relay willoperate in response to said predetermined electrical current.
 2. Acurrent-sensing relay as set forth in claim 1 wherein: said blade iselongated, flexible and crooked and has one end affixed to said housingand carries said movable contact on its free end; and said actuatormeans operatively engages said blade intermediate said one end and saidmovable contact to move said free end transversely and engage saidmovable contact with said first contact, and then continue transversemovement of the intermediate portion of said blade to further flex saidblade and slide said movable contact across said first contact a slidingdistance greater than it would be slid by an equivalent amount oftransverse movement of the intermediate portion of a straight bladewhereby when said actuator is released said blade will unflex and movesaid movable contact said sliding distance across said first contact toprovide a relatively large contact breaking force.
 3. A current-sensingrelay as set forth in claim 1 wherein: said amplifier means includes asilicon-controlled rectifier having its gate in circuit with saidsensing means and its power circuit in circuit with said actuator means.4. A current-sensing relay as set forth in claim 1 wherein: saidactuator means includes an arm having its front extremity projectingover said blade for engagement therewith, a mount carried on saidhousing for supporting the rear extremity of said arm and including aresilient holding clip projecting forwardly over the rear extremity ofsaid arm and beyond said mount to bias said front extremity downwardlytoward said blade.
 5. A current-sensing relay as set forth in claim 1wherein: said housing includes a terminal receiving passage formed witha depression in one side for defining a keyway; and said relay includesa plug terminal in circuit with one of said contacts and projectingthrough said passage to form a plug prong, said terminal being formedwith a reduced-in-cross-section portion defining a key forcomplimentally interfitting said keyway whereby said terminal may beinserted in said passage, shifted laterally therein to fit said key insaid keyway, and affixed to said housing to mount said terminal firmlyon said housing.
 6. A current-sensing relay as set forth in claim 1wherein: said housing is formed with a terminal receiving passage; andsaid relay includes a terminal for insertion in said passage andincluding a malleable rivet forming portion whereby said terminal may beinserted in said passage and said rivet forming portion riveted over tohold said terminal captive in said passage.
 7. A current-sensing relayas set forth in claim 1 wherein: said housing includes a base formedwith a pair of oppositely disposed sidewalls formed on their exteriorwith respective clip-receiving recesses, said housing further includinga cover formed with a pair of oppositely disposed downwardly projectingsidewalls in juxtaposition with the walls of said base and formed withresilient clips for receipt in said recesses to lock said cover to saidbase.
 8. A current-sensing relay as set forth in claim 1 wherein: saidhousing includes a blade mount; said actuator includes an arm formed onits rear extremity with a pair of spaced apart legs carried on saidmount, and is formed intermediately with a downwardly projecting apex;and said housing includes a stop disposed adjacent said apex forengagement thereby to limit travel of said arm toward its contactclosing position whereby said arm will be supported at three points whensaid relay is actuated.
 9. A current-sensing relay as set forth in claim1 that includes: a bobbin formed with a spool for winding said coilthereon and with a passage extending through the center of such spoolfor receipt of a magnetic conductor disposed in electrical inductiverelationship with said lead.
 10. A current-sensing relay as set forth inclaim 2 wherein: said blade is formed intermediately with apeg-receiving opening; and said actuator means includes a peg whichloosely interfits said opening whereby the intermediate portion of saidblade will be free to shift forwardly and rearwardly during actuation ofsaid relay to facilitate alignment between said blade and actuator. 11.A current-sensing relay as set forth in claim 1 wherein: said housingincludes a mounting bar having its opposite ends connected with saidloop and having said coil wound therearound.
 12. A current-sensing relayas set forth in claim 11 wherein: said housing is formed with a pair ofslots for receiving the opposite extremities of said loop; said loop isgenerally U-shaped and has its opposite extremities projecting throughsaid slots and said opposite extremities are formed with openings; andthe opposite extremities of said mounting bar project through saidopenings and are secured to said housing to affix said loop to saidhousing.
 13. A current-sensing relay as set forth in claim 9 wherein:said actuator means includes a plurality of electrical components; andsaid bobbin includes a plurality of holding tabs forming cavities forreceipt of said respective components.
 14. An electrical switch as setforth in claim 1 wherein: said actuator means includes an electromagnethaving its core formed on one end with a stop, an arm coupled with saidblade and overlying said core and formed with a V-shaped ferromagneticportion disposed adjacent said stop and having its apex engageabletherewith when said electromagnet is energized whereby said V-shapedportion will form a plate for a relatively large portion of the magneticflux from said electromagnet thereby leaving a relatively small portionof the magnetic flux to assume a path across the composite airgapbetween said V-shaped portion and said stop.
 15. A current-sensing relayas set forth in claim 1 that includes: a second contact mounted fromsaid housing, disposed on the opposite side of said blade from saidfirst contact, and in engageable alignment with said movable contact.16. A current-sensing relay as set forth in claim 1 that includes: anauxiliary plug terminal mounted on said housing and connected in circuitelectrical actuator for connection to a lead from an auxiliary actuatorwhereby said relay may be actuated by said auxiliary actuator.